Christian, Thanks again! the last 2 commits in vfs.pidfd look good to me. As for this patch, I am not sure I understand your concerns, and I have another concern, please see below. For the moment, please forget about PIDFD_THREAD. On 02/10, Christian Brauner wrote: > > (1) kill(-1234) => kill process group with id 1234 > (2) kill(0) => kill process group of @current > > which implementation wise is indicated by > > __kill_pgrp_info(..., pid ? find_vpid(-pid) ? task_pgrp(current)) > > We're obviously not going to implement (2) as that doesn't really make a > sense for pidfd_send_signal(). Sure, > But (1) is also wrong for pidfd_send_signal(). If we'd ever implement > (1) it should be via pidfd_open(1234, PIDFD_PROCESS_GROUP). Why do you think we need another flag for open() ? To me it looks fine if we allow to send the signal to pgrp if flags & PIDFD_SIGNAL_PROCESS_GROUP. And pidfd_send_signal() can just do if (PIDFD_SIGNAL_THREAD_GROUP) ret = __kill_pgrp_info(sig, kinfo, pid); else ret = kill_pid_info_type(...); (yes, yes, this needs tasklist, just a pseudo code to simpliy) Now lets recall about PIDFD_THREAD. If the target task is a group leader - there is no difference. If it is not a leader - then __kill_pgrp_info() will always return -ESRCH, do_each_pid_task(PIDTYPE_PGID) won't find any task. And personally I think this is all we need. ------------------------------------------------------------------------------ But if you want to make PIDFD_SIGNAL_THREAD_GROUP work even if the target task is not a leader, then yes, we need something like task_pgrp(pid_task(pid, PIDTYPE_PID)) like you did in the new kill_pgrp_info() helper in this patch. I won't argue, but do you think this makes a lot of sense? Oleg.
